Add tsan support to v8's gyp and test driver.

build/standalone.gypi

Index: build/standalone.gypi
diff --git a/build/standalone.gypi b/build/standalone.gypi
index 932a4686a3ebe3d15824425ab4602836507e8ad0..1fcb8860b4d10e813358b6360699883ce85f4807 100644
--- a/build/standalone.gypi
+++ b/build/standalone.gypi
@@ -35,6 +35,7 @@
     'component%': 'static_library',
     'clang%': 0,
     'asan%': 0,
+    'tsan%': 0,
     'visibility%': 'hidden',
     'v8_enable_backtrace%': 0,
     'v8_enable_i18n_support%': 1,
@@ -186,6 +187,27 @@
         ],
       },
     }],
+    ['tsan==1', {
+      'target_defaults': {
+        'cflags+': [
+          '-fno-omit-frame-pointer',
+          '-gline-tables-only',
+          '-fsanitize=thread',
+          '-fPIC',
+          '-Wno-c++11-extensions',
+        ],
+        'cflags!': [
+          '-fomit-frame-pointer',
+        ],
+        'ldflags': [
+          '-fsanitize=thread',
+          '-pie',
+        ],
+        'defines': [
+          'THREAD_SANITIZER',
+        ],
+      },
+    }],
     ['OS=="linux" or OS=="freebsd" or OS=="openbsd" or OS=="solaris" \
        or OS=="netbsd"', {
       'target_defaults': {